Brake parts questions on a 79 sierra.

[Retoxtony]

Hopefully a easy question for someone here. Are brake parts like calipers and pads the same for trucks with the HD (1.25) rotors vs the smaller ones? I was ordering some parts this morning and both at Napa and then on Rock Auto they dont differentiate between them. Unless I’m missing something obvious here? Or do all trucks of some years have the fatter rotors?

I am in the process of lowering this truck and it’s turned into a full rebuild of the front end. I figured while I have everything apart I might as well do the brakes as well.

 

[Bextreme04]

There is difference in pads between JB5, JB6, and JB7 brakes. It is not expressly related to rotor thickness. What RPO brakes do you have?

 

[AuroraGirl]

I could be wrong with this but 1979 i BELIEVE is the first year for metric GM brakes which maybe it was 81 Im not so certain, but i believe rotor differences could be for a larger rotor, thickness wise, but not radially, had a dual piston or perhaps still 1 piston caliper but with more surface area of pad. Alternatively, the weigjht range of the truck or some option may have designated larger cooling vane size and thats why. I read way too much abotu the subject for my car and forgot the truck specifics.
edit: that reminds me, the front brakes im pretty sure are important to make sure it stays right because half ton truck is gonna be semi floating front while full floating for a 3/4 ton, which is one thing that would be a jump in rotor diameter. im assumign you are only talking about offerings for 3/4 ton but thought to mention it

 

[Retoxtony]

There is difference in pads between JB5, JB6, and JB7 brakes. It is not expressly related to rotor thickness. What RPO brakes do you have?

RPO codes are JB5 and J55. So it’s the 1.25” HD brakes.

The issue I’m having is when I call for brake parts for a 79 GMC they tell me they don’t list different pads, calipers, etc for different RPO codes or 1.25” rotors vs 1”. The parts guy at NAPA flat out told me that 79 GMC trucks only have one size set of brakes. I told him I’m pretty sure he’s wrong, but that’s why I’m here asking. I just really hate ordering the wrong parts.

 

[Bextreme04]

RPO codes are JB5 and J55. So it’s the 1.25” HD brakes.

The issue I’m having is when I call for brake parts for a 79 GMC they tell me they don’t list different pads, calipers, etc for different RPO codes or 1.25” rotors vs 1”. The parts guy at NAPA flat out told me that 79 GMC trucks only have one size set of brakes. I told him I’m pretty sure he’s wrong, but that’s why I’m here asking. I just really hate ordering the wrong parts.

1.25" brakes means nothing... all pre-80's C10's had 1.25" rotors. In fact... all C10's before the 80's had the same front rotor size. The J55 option just means you have power brakes, since the standard was manual brakes with no booster. Having the higher gross weight meant you got those RPO codes standard.

Here's a thread from a few years ago talking about this specifically. I would scroll all the way to the end, the front has a lot of conjecture and wrongful speculation. Keith comes in at the end with the real info(he worked in the truck assembly line back in the day).
https://www.gmsquarebody.com/threads/rpo-j55.21924/page-2

 

[Retoxtony]

1.25" brakes means nothing... all pre-80's C10's had 1.25" rotors. In fact... all C10's before the 80's had the same front rotor size. The J55 option just means you have power brakes, since the standard was manual brakes with no booster. Having the higher gross weight meant you got those RPO codes standard.

Here's a thread from a few years ago talking about this specifically. I would scroll all the way to the end, the front has a lot of conjecture and wrongful speculation. Keith comes in at the end with the real info(he worked in the truck assembly line back in the day).
https://www.gmsquarebody.com/threads/rpo-j55.21924/page-2

Thanks, that’s pretty helpful. I had no idea all pre-80s had the thicker rotors but that alone answers a few questions I had in my head. I’d assume all calipers from those trucks should be the same then as well? If that’s the case I’ll just order some from Rock Auto.

 

[AuroraGirl]

Thanks, that’s pretty helpful. I had no idea all pre-80s had the thicker rotors but that alone answers a few questions I had in my head. I’d assume all calipers from those trucks should be the same then as well? If that’s the case I’ll just order some from Rock Auto.

Does that apply to K10 too? Just wondering

Also sorry OP just occured to me youre talking 2wd fronts RIP

 

[Grit dog]

I could be wrong with this but 1979 i BELIEVE is the first year for metric GM brakes which maybe it was 81 Im not so certain, but i believe rotor differences could be for a larger rotor, thickness wise, but not radially, had a dual piston or perhaps still 1 piston caliper but with more surface area of pad. Alternatively, the weigjht range of the truck or some option may have designated larger cooling vane size and thats why. I read way too much abotu the subject for my car and forgot the truck specifics.
edit: that reminds me, the front brakes im pretty sure are important to make sure it stays right because half ton truck is gonna be semi floating front while full floating for a 3/4 ton, which is one thing that would be a jump in rotor diameter. im assumign you are only talking about offerings for 3/4 ton but thought to mention it

???

 

[Turbo4whl]

Okay, my '82 came with semi-metallic front brake pads. Since I play hard, I warped the front rotors before I wore out the pads. Cut and trued the original rotors and bought the soft pads (organic). I put 200,000 miles on those same rotors. Yes, had to change the pads sooner but didn't warp the rotors again.

Your truck takes D-52 pads. Friction material, your choice. Parts people only know what is in their list.

 

[MikeB]

My 82 C10 had 1" thick rotors, which also means different caliper, spindle, and inner wheel bearing. Pads are the same as 1.25" brakes.

My 69 C10 has 1" brakes & spindles from an 85 C10, but they work great. Only advantage of the thicker rotor is better heat dissipation for downhills and towing.